As described in applicant's prior application, Ser. No. 88,197, it has been well known in the welding industry in general and the can or container welding industry in particular that it is difficult to butt weld the sheared or slit edges of tinplate or other sheet metal in a substantially continous welding operation. In applicant's prior application, however, a three-piece Z-Bar apparatus was described which could be used for continously lap welding sheet material and also disclosed a method for permitting the opposed edges of the overlapped sheet material to be diverged relative to one another as they entered a high energy welding zone whereby the material would be essentially in edge-to-edge relationship at the point of the weld so that a butt welded seam could be created. Obtaining continously satisfactory results in creating acceptable butt welded seams by controlled diverging of the opposed sheet metal edges is somewhat difficult, however.
Other prior art developments have been made in the high energy welding of sheet metal and particularly sheet metal containers. In U.S. Pat. No. 4,152,573 to Saurin et al, a device and method for manufacturing cans using laser welding is disclosed. As discussed in that patent, it would be advantageous to form containers using butt welded seams rather than overlapped seams, particularly due to the problems encountered with forming the container top and bottom due to the increased material thickness along the line of the weld. In Saurin et al, a technique of butt welding is disclosed wherein the opposed edges of the sheet metal are held together in edge-to-edge relationship by special clamping members or vises. In such a method and in using such an apparatus, the high energy welding procedures must be interrupted after each container is welded so that another sheet of material can be wound and clampingly engaged between the vise-like members. Thus, such a process although providing a desired butt welded product, does so only with significant increase in time and therefore expense.
Additionally, there are other problems associated with conventional type Z-Bar Guides used in the welding industry. Not only do such problems include time and cost concerning machinery, repair or replacement, but such conventional structures have not been specifically adapted or designed to provide for the continuous butt welding of sheet metal stock to form such cylindrical products as cans, containers and the like. Some other examples of prior art disclosures include U.S. Pat. Nos. 2,883,956; 3,834,010 and 4,145,986 and Federal Republic of Germany Offenlegungsschrift 24 26 379 (Feb. 1, 1975).